The Hybridoma Facility of the Laboratory of Cellular Physiology collaborates with numerous laboratories in FDA, NIH and other institutions in the production and characterization of monoclonal antibodies (MAbs). During this reporting period, the Facility has conducted or assisted in fourteen hybridoma fusions, eight related procedures from previously completed fusions and initiated procedures for three additional fusions scheduled during this reporting period. These fusions required screening by ELISA or Western blot of approximately 1790 wells of culture fluid by the Facility or its collaborators. As a result, almost 150 lines have been selected for further study and subsequently expanded in order to allow for frozen storage. These fusions included a procedure where spleens of two animals immunized with different antigens were fused in parallel and one where cells of Peyers patches were substituted for spleen cells. Reagents produced in this Facility have been used in six of seven DBP laboratories and have had a significant impact on research projects and regulatory matters. One MAb is the subject of a patent application for the development of a diagnostic kit for the detection of infection with the AIDS virus.